A molecular investigation of genotype by environment interactions.
A molecular investigation of genotype by environment interactions.
复制标题
通过环境相互作用对基因型进行分子研究。
DOI：
10.1093/genetics/139.1.19
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发表时间：
1995
期刊：
影响因子：
3.3
通讯作者：
Dean,AM
中科院分区：
文献类型：
--
作者：
Dean,AM
7个乳糖操纵子的适应度是在竞争限制生长速率的半乳糖-甘油（一种天然存在的半乳糖苷）的过程中确定的，这些操纵子被转导到大肠杆菌天然分离株的共同遗传背景中。这些操纵子在乳糖和三种人工半乳糖糖（乳果糖、甲基半乳糖糖和半乳糖糖-阿拉伯糖）上的适用性已经被确定。分析表明，虽然环境相互作用会产生显著的基因型，但适应度排名的变化很少。测定了半乳糖-甘油、乳糖、乳果糖和甲基半乳糖苷对β -半乳糖苷酶和透膜酶的相对活性。两种酶都表现出相当大的动力学变化。β -半乳糖苷酶等位基因在酶活性水平上没有提供环境相互作用的基因型证据。渗透酶等位基因表现出的基因型受环境相互作用的影响，少数等位基因的活性排序发生变化。通过代谢控制分析，对透膜酶和β -半乳糖苷酶对适应度的贡献进行了划分。适应度水平上受环境相互作用的基因型大多数是由通路中各步骤间控制分布的变化产生的，特别是在渗透酶，大的控制系数确保其动力学变异具有显著的适应度效应。事实上，运动排名的变化可以解释健身排名的少数变化。相比之下，β -半乳糖苷酶的控制系数足够小，其动力学变化处于或接近中性极限。由于渗透酶和β -半乳糖苷酶的控制系数较大，人工半乳糖苷的选择系数较大。通量求和定理要求与通路中其他步骤相关的控制系数必须减小，这意味着这些步骤对人工半乳糖苷的选择强度较小。这表明，在新的环境中，选择强度不必更大。
The fitnesses conferred by seven lactose operons, which had been transduced into a common genetic background from natural isolates of Escherichia coli, were determined during competition for growth rate-limiting quantities of galactosyl-glycerol, a naturally occurring galactoside. The fitnesses of these same operons have been previously determined on lactose and three artificial galactosides, lactulose, methyl-galactoside and galactosyl-arabinose. Analysis suggests that although marked genotype by environment interactions occur, changes in the fitness rankings are rare. The relative activities of the beta-galactosidases and the permeases were determined on galactosyl-glycerol, lactose, lactulose and methyl-galactoside. Both enzymes display considerable kinetic variation. The beta-galactosidase alleles provide no evidence for genotype by environment interactions at the level of enzyme activity. The permease alleles display genotype by environment interactions with a few causing changes in activity rankings. The contributions to fitness made by the permeases and the beta-galactosidases were partitioned using metabolic control analysis. Most of the genotype by environment interaction at the level of fitness is generated by changes in the distribution of control among steps in the pathway, particularly at the permease where large control coefficients ensure that its kinetic variation has marked fitness effects. Indeed, changes in activity rankings at the permease account for the few changes in fitness rankings. In contrast, the control coefficients of the beta-galactosidase are sufficiently small that its kinetic variation is in, or close to, the neutral limit. The selection coefficients are larger on the artificial galactosides because the control coefficients of the permease and beta-galactosidase are larger. The flux summation theorem requires that control coefficients associated with other steps in the pathway must be reduced, implying that the selection at these steps will be less intense on the artificial galactosides. This suggests that selection intensities need not be greater in novel environments.